In many areas of engineering, hydraulic pressure receivers are used which are capable of receiving changing external ratios of load and transmitting them to a suitable measuring instrument or recording means or ac-vf converter. For this, an incompressible fluid, such as water, is found in a compressible housing of, for example, rubber-like material, which is connectable to the measuring means.
It has become apparent with such pressure receivers that only very short, compact pressure receivers, by which the compressive load can take place evenly over the whole length of the housing, pass precise and always constant relative pressure values to the measuring means, as such pressure receivers function as hydrostatic piston-cylinder systems.
However, as soon as a tubular-shaped housing of a relatively great length is used, as is required, for example for the monitoring of changes of pressure over large distances or surface areas, great deviations in the measured relative pressure values occur by the same compressive load on the housing and, that is, in dependence on the distance of the area receiving the load from the point of attachment of the elastic pressure receiver housing on the measuring means.
The reason for this is the elastic housing's no longer being even over its whole extent but now point loaded, which, under the inward deformation of a part of the housing wall, the displaced fluid is able to flow to another place owing to the outward deformation on the housing wall, and, moreover, the pressure impulse continues wave-like in the fluid, whereby the wave energy, as is generally known, diminishes by the square of the distance from the wave centre (pressure impact point). The farther the distance, therefore, of the pressure impact on the housing wall from the load-receiving point of the elastic pressure receiver on the measuring means takes place, so the smaller the measured relative pressure becomes. This restricts, of course, the scope of application of such hydraulic pressure receivers by a considerable extent.